1. Field of the Invention
The present invention pertains generally to the field of medical devices and more specifically to a system to an improved system for delivering therapy.
2. Background
Atrial fibrillation (AF) affects 2-3 million Americans, costing the healthcare system an estimated $6.65 billion per year to treat. When a patient has AF, the normal depolarizing wave that produces near synchronous activation of cardiac cells in the atrial chambers of the heart is disrupted and coordinated activity ceases. When this occurs, the blood pools in the atrial chambers and does not eject effectively into the ventricles, leading to fatigue, dizziness, nausea, increased risk of clot formation and stroke, and ultimately heart failure.
Normally, the depolarization wave that produces atrial contraction is initiated by pacemaker cells in the sinoatrial (SA) node in the right atrium. In patients suffering from AF, groups of cardiac cells outside the SA node become hyperactive and produce secondary depolarization wave fronts that interact with the normal depolarization wave front, leading to chaotic timing of cardiac cell contractions. Initially, the AF episodes may be few and far between, with the heart able to recover on its own (Paroxysmal AF), but left untreated, the episodes become more frequent and ultimately transition toward Persistent AF, a condition much more difficult to treat. The AF triggering foci responsible for producing atrial fibrillation are located in the pulmonary veins (PV) in the vast majority of cases.
One of the most common procedures for preventing future AF events from occurring is radiofrequency (RF) catheter ablation or cardiac ablation. The goal of cardiac ablation is to electrically ablate and/or isolate AF triggering foci from the rest of the heart to prevent an AF occurrence. Cardiac ablation can be performed epicardially through open heart surgery, via small chest incisions, or endocardially via a catheter-based approach. Catheter-based ablation is the least invasive and is therefore preferable to minimize recovery times and infection rates. In catheter-based ablation, a catheter is fed through a blood vessel in the groin up into the heart and across the septum into the left atrium. The catheter has a metallic tip that is used to deliver high frequency electrical current to tissue. The current locally heats up (ablates) the tissue and as the ablation catheter tip is moved across the tissue it creates a variety of lesion patterns that performs a conduction block to isolate AF trigger foci from the remaining healthy heart tissue. Inconsistent and unstable placements of the ablation catheter tip during the procedure can result in lesion patterns that are disjointed and/or of insufficient ablation depth to be effective. In patients with Paroxysmal AF, catheter ablation to isolate the pulmonary veins is 60-80% successful in eliminating AF. Patients with long-term, persistent AF have poorer and more variable outcomes from a single ablation procedure (30-50% success rates). In this cohort, significant remodeling of the atria has occurred and more extensive and complicated ablation patterns may be required to isolate all of the AF sources. Thus, it is estimated a single catheter ablation procedure is successful in long-term elimination of AF in only 30-80% of patients.
Minimally-invasive procedures require deployment of surgical tools and effectors through small incisions in the body and/or in conjunction with other medical instruments. One example of a system for delivery therapy is found in U.S. Pat. No. 8,100,900 to Prinz et al., the contents of which are incorporated by reference herein in their entirety for all purposes.
Referring to prior art FIG. 1, Prinz et al. describes a system for delivering therapy in which a set of gears 2 contained within an end effector 1 rotate inwardly, in opposite directions, in order to grip a section of tissue and provide continuous motion. Once the tissue is gripped, therapy is applied to it. In the case of AF cardiac ablation, the therapy consists of radiofrequency electrical current used to selectively ablate the cardiac tissue, conducted through an electrode 4. All components of the end effector 1 are situated within a housing 3, attached at the distal end of a catheter 5. At the proximal end of the catheter 5, the operator controls the device. This patent application illustrates several novel embodiments to further advance these procedures.
Many procedures utilize flexible steerable catheters to access the treatment areas. With existing catheter-based devices, it is cumbersome to manipulate the distal tip to create adjacent or contiguous lesions or perform other local treatment. The challenge is exacerbated when the target organ tissue is also contracting and/or moving due to respiration, cardiac function, peristalsis or other bodily movement. Other procedures utilize medical instruments (e.g., endoscopes) with small working channels and/or size constraints because of organ size. Holding position during procedures with these medical instruments is extremely difficult due to patient movement, respiration, peristalsis, and other bodily movements. Clinicians often spend several minutes searching for their lost target—reducing the accuracy and effectiveness of treatment. Thus, what is needed is a device capable of gripping tissue, then holding the tissue in position, without negatively impacting the procedure or tissue.
Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the invention.